As is known, the switching activity on a wide bus or a narrow bus is responsible for a non-negligible absorption of electrical energy by the bus.
A bus can in fact be considered as a set of transmission lines, to each of which there is associated a parasitic capacitance, which, at each switching of the corresponding line, i.e., at each transition 0→1 or 1→0 of the signals travelling thereon, must be charged or discharged, with consequent absorption of electrical energy.
Reduction of bus switching activity is hence an issue to which there has been dedicated, and there continues to be dedicated, an intense and extensive research activity aimed at reducing the absorption of electrical energy and, more in general, at preventing the adverse phenomena linked to the capacitive behaviour of the bus.
A technique that is widely used for reducing bus switching activity consists in encoding the data stream to be transmitted on the bus using an invertible encoding law, i.e., one that can be decoded.
The encoding technique known as “bus-inverted” technique is currently the one most widely used for reducing bus switching activity, both on account of its ease of implementation, and on account of the good performance achieved, especially where the total number of lines of the bus is small. This encoding further proves to be usable also on asynchronous buses.
For a more detailed review of the subject, the following works may be usefully consulted: Adaptive Bus Encoding Technique for Switching Activity Reduced Data Transfer over Wide System Buses, Claudia Kretzschmar, Robert Siegmund and Dietmar Müller, International Workshop—Power and Timing Modelling, Optimization and Simulation (PATMOS2000) Goettingen (D), Sep. 13-15, 2000; and Architectures and Synthesis Algorithms for Power-Efficient Bus Interfaces, I. Benini, A. Macii, E. Macii, M. Poncino, R. Scarsi, IEEE Transactions on CAD, Vol. 19, No. 9, September, 2000, pp. 969-980.